1. Field of the Invention
The present disclosure relates to a communication system, and in particular, but not exclusively, to transferring a user equipment from a network to another network in a communication system, said other network providing sharable network resources.
2. Description of the Related Art
A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes associated with the communication system. The communication may comprise, for example, communication of voice, data, multimedia and so on. A user equipment connected to a communication system may, for example, be provided with a two-way telephone call or multi-way conference call or with a data connection. A user equipment may communicate packet data to and from a server entity, or between two or more user equipments.
A communication system typically operates in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standard or specification may define if a user equipment is provided with a circuit switched service or a packet switched service or both. Communication protocols and/or parameters which shall be used for the connection are also typically defined. For example, the manner how the user equipment can access the communication system and how communication shall be implemented between the user equipment and the elements of the communication network is typically based on predefined communication protocols. In other words, a specific set of “rules” on which the communication can be based on needs to be defined to enable the user equipment to communicate via the communication system.
Communication systems proving wireless communication for user equipment are known. These systems are commonly referred to as mobile systems, although in certain systems the mobility may be restricted to substantially small areas. An example of the mobile systems is the public land mobile network (PLMN). A PLMN is commonly based on cellular architecture. Another example is a mobile system that is based, at least partially, on use of communication satellites. Mobile communications may also be provided by means of other mobile systems, such as by means of wireless local area networks (WLAN).
In a common wireless system a base station servers a plurality of user equipment. A user equipment may also be in wireless communication with two or more base stations at the same time. Communication on the wireless interface between the user equipment and the base station can be based on an appropriate communication protocol. A base station is understood to be a part of an access network (AN) that enables the mobile station to access the core part of the communication network, referred to as the core network (CN).
The skilled person knows the basic operational principles and elements required for the wireless access. Examples of these include access systems such as the CDMA (Code Division Multiple Access), WCDMA (Wide-band CDMA), TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), or SDMA (Space Division Multiple Access) and hybrids thereof.
Each base station and/or access network is controlled by an appropriate control arrangement. The operation of a base station and other apparatus of the access network can be controlled by one or several control entities. Two or more base stations may be controlled by a controller. For example, the third generation (3G) Wideband Code Division Multiple Access (WCDMA) networks employ control entities known as radio network controllers (RNC) for controlling the operation of the wireless access network. In the second generation (2G) GSM (Global System for mobile) the access network is understood to be controlled by a base station controller (BSC). A radio network controller may control a number of stations, or all stations, of an access network.
The access network controllers are connected to appropriate core network entities. One or more gateway nodes may also be provided for connecting a core network to other networks. For example, a mobile core network may be connected to other mobile or fixed line communication networks or communication networks such as an IP (Internet Protocol) and/or other packet data networks.
A communication network is commonly run and operated by a network operator. The operation environment of network operators has changed and is becoming more dynamic in its nature. For example, partnerships, acquisitions, creative agreements among operators and so on have forced the operators to rethink the way they use the resources of their networks. The changes have opened the minds for the possibility of sharing the networks resources. However, there are some technical obstacles before more dynamic operation and sharing of the resources could become reality, not least because of the way the technical aspects of the networks are standardised.
The concept of “network sharing” shall be understood broadly, and includes various scenarios, for example, but not limiting to these, a common radio access network connected to a multiple core networks, multiple radio access networks sharing one core network, or multiple radio access networks connected to a multiple of core networks.
Conventionally telecommunications service providers have operated and owned their networks. Use of a network by a party other that the owner of the network has been enabled by means of roaming agreements or the like. For example, when the GSM and then the UMTS systems were specified, the possibility of sharing part or the entire network by two or more separate commercial entities was not considered at all. GSM was designed under the principle “one operator, one radio access network”. Although the GSM network has some possibilities of infrastructure sharing, it does not properly support sharing of resources at the radio access network level. The initial design of third Generation Partnership Project (3GPP) systems has followed the same principle. As a result the standards lack functionalities that could enable the realization of such commercial agreements, and more efficient use of the resources.
Proposals for network-sharing include the scenarios such as the Gateway Core Network (GWCN) and the Multiple Operator Core Network (MOCN). The GWCN scenario is intended for legacy-shared networks, and defines how a gateway core network can be deployed for shared-network architecture where, besides the radio access network, mobile switching centres (MSCs) and serving GPRS (general packet radio service) support nodes (SGSNs) are also shared. The GWCN scenario also describes how the scenario might be deployed with functionalities of older networks. It also allows the radio access network operator to be or not to be one of the core network operators.
One recent improvement for the GWCN scenario is the possibility to select a network by a user equipment. In this scenario the user equipments can be made aware of the operators providing services in the shared network. A supporting user equipment for use in this scenario may be any equipment which is capable of understanding information about available operators as provided by the shared network, selecting one of the available operators, and indicating the selected operator to the network.
User equipments that are supporting shared networks are a fairly recent proposal. Therefore a number of non-supporting user equipment will be in use for the foreseeable future. When a user equipment that is not supporting network sharing is being transferred from an access network to another, the target shared access network controller should include a commonly used operator identity that is understood by such a user equipment. In certain systems, for example those based on 3G standards, radio access network provides a globally unique location information to a user equipment when it is transferred from an access network to another. Thus, the location information contains a PLMN identity as part of the location information. In a communication system employing sharing of network resources a question is which PLMN identity is provided to the user equipment, since there are a multiple of choices, due to a multiple of operators providing service in the same physical network. It has been proposed that for a non-supporting user equipment, the PLMN identity should be the identity of the radio access network (Common-PLMN-ID), and not the identity of any of the possible operators.
However, the access network controller does not necessarily know if a user equipment is configured such that it can support sharing of network resources. Thus the controller may not know to which user equipments it should include information regarding the identity of the possible serving network.
In addition to this, when handing over or relocating a user equipment from a non-shared network to a shared network with GWCN configuration, the target shared access network controller may not necessarily know which one of the PLMNs of the network should be serving the user equipment.
It shall be appreciate that the problem is not limited to transfer from a non-shared to shared network. Similar problem may occur within a shared network.
A user equipment may be transferred from an access system to another, for example in handover or relocation. It is technically possible that a user equipment that supports network sharing registers to a different core network operator for packet switched domain than the one serving the user equipment for an ongoing circuit switched connection. This may not always be desirable.
A user equipment is RRC-connected after a handover, and thus it may not have to include a core network identity in a message such as the ‘INTIAL DIRECT TRANSFER’ message to access network controller, because the access network should already know what is the identity of the selected PLMN. However, the access network controller needs to know in that case the selected PLMN for the user equipment, because it may need to indicate it to the user equipment and also because it may need to store it so that the access network controller is able to indicate the identity to the shared SGSN in the case of GWCN, when NAS-RAU has to be sent via RANAP:INTIAL UE MESSAGE (after reception from user equipment of the RRC:INTIAL DIRECT TRANSFER message, which does not include the identity because the user equipment is RRC-connected). Furthermore, after circuit switched handover from non shared network or another shared access controller, the access network controller is mandated, in order to allow the user equipment to register on a packet switched domain, to send the RRC:UTRAN MOBILITY INFORMATION to the user equipment, which includes the core network Information Info that indicates the current Selected PLMN to the user equipment. The supporting user equipment may need to get the right PLMN identity because it may need to use it later on when the circuit switched call is released and the user equipment goes back to idle. In that case the user equipment may perform background scan and check whether its current selected PLMN is the right high priority PLMN. If not the user equipment may perform another routing area update (RAU). If the access network controller sends to user equipment a Common PLMN-ID instead of a selected CN-PLMN-ID in the core network information info in UTRAN MOBILITY INFORMATION, the user equipment will almost always performs a RAU after the circuit switched call is released, leading to significant increase in signaling.
Therefore there is a need for an improved solution for the handling of handovers or other relocations of user equipment in communications systems including at least one shared network.